Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$119.98	12.445%	$134.9115	$134.91	$134.90	$134.90
Purchase #2	$38.42	6.725%	$41.0037	$41.00	$41.00	$41.00
Purchase #3	$90.27	5.460%	$95.1987	$95.20	$95.20	$95.20
Purchase #4	$34.36	4.326%	$35.8464	$35.85	$35.85	$35.80
Purchase #5	$91.37	6.538%	$97.3438	$97.34	$97.35	$97.30
Purchase #6	$73.89	5.711%	$78.1099	$78.11	$78.10	$78.10
Purchase #7	$247.81	10.784%	$274.5338	$274.53	$274.55	$274.50
7 purchase totals =	$696.10		$756.9478	$756.94	$756.95	$756.80